Biologic and Clinical Characteristics of Breast Cancer With Single Hormone Receptor–Positive Phenotype

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Abstract
Purpose: Response to endocrine therapy in breast cancer correlates with estrogen receptor (ER) and progesterone receptor (PgR) status. It is usually easier to decide treatment strategies in cases of double-positive/-negative phenotypes than in single-positive tumors. Patients and Methods: We have examined a large and well-characterized series of primary invasive breast carcinoma (1,944 cases) with long-term clinical follow-up and hormone therapy data. Patients were stratified according to ER and PgR expression and the study was focused on the single-positive groups (ER–/PgR+ and ER+/PgR–), to assess their main features and evaluate any prognostic and predictive difference between them and compare them with the double-positive/-negative tumors. Results: ER+/PgR–tumors were found more frequently in elderly, postmenopausal women. The majority were grade 2 ductal/no specific type carcinomas. There was no difference between the two groups with regard to lymph node stage. Survival analyses showed no difference between the two groups in terms of disease-free interval and overall survival. However, when compared with the double-negative phenotype, ER+/PgR–showed an association with better outcome but no such survival advantage was detected in case of ER–/PgR+ tumors. In the group of patients with ER+ tumors who received adjuvant hormonal therapy, absence of PgR (ER+/PgR–) was an independent predictor of development of recurrence and shorter survival and, hence, poorer response to hormonal therapy. Conclusion: ER+/PgR–and ER–/PgR+ tumors are biologically and clinically distinct groups of breast cancer that may require different treatment strategies with ER–/PgR+ exhibiting more aggressive behavioral characteristics.